NAME
t_open() — establish a transport endpoint
SYNOPSIS
#include <fcntl.h>
#include <xti.h> /* for X/OPEN Transport Interface - XTI */
/* or */
#include <tiuser.h> /* for Transport Layer Interface - TLI */
int t_open (name, oflag, info);
char *name;
int oflag;
struct t_info *info;
DESCRIPTION
The
t_open()
function must be called as the first step in the initialization
of a transport endpoint. This function establishes a transport
endpoint by opening a file that identifies a particular transport
provider and returning a file descriptor that identifies that endpoint.
The argument
name
points to a file name that identifies a transport
provider. When using HP XTI to connect to the OSI protocol stack,
name
must be
/dev/ositpi
for the connection-mode service, or
/dev/osicltpi
for the connectionless service. When using HP XTI to connect
to the TCP protocol stack,
name
should be
/dev/tcp.
For UDP,
name
should be
/dev/udp.
(See also the
OBSOLESCENT INTERFACES
section.)
For TLI, use the device file name of the transport provider desired.
Note that HP TCP/UDP/IP and HP OSI COTS and CLTS only support XTI.
oflag
identifies any open flags (as in
open())
and is constructed from
O_RDWR
optionally or-ed with
O_NONBLOCK.
These flags are defined by the header file
<fcntl.h>.
t_open()
returns a file descriptor that will be used by all subsequent functions
to identify the particular local transport endpoint.
This function also returns various default characteristics of the
underlying transport protocol by setting fields in the
t_info
structure. This argument points to a
t_info
which contains the following members:
t_scalar_t addr; /* max size of the transport protocol */
/* address */
t_scalar_t options; /* max number of bytes of */
/* protocol-specific options */
t_scalar_t tsdu; /* max size of a transport service data */
/* unit (TSDU) */
t_scalar_t etsdu; /* max size of an expedited transport */
/* service data unit (ETSDU) */
t_scalar_t connect; /* max amount of data allowed on */
/* connection establishment functions */
t_scalar_t discon; /* max amount of data allowed on */
/* t_snddis and t_rcvdis functions */
t_scalar_t servtype; /* service type supported by the */
/* transport provider */
t_scalar_t flags; /* other info about the transport provider */
The values of the fields have the following meanings:
- addr
A value greater than or equal to zero indicates the maximum size of a
transport protocol address.
A value of -1 specifies that there is no limit on the address size.
A value of -2 specifies that the transport provider does not provide
user access to transport protocol addresses.
- options
A value greater than or equal to zero indicates the maximum number of
bytes of protocol-specific options supported by the provider.
A value of -1 specifies that there is no limit on the option size.
A value of -2 specifies that
the transport provider does not support user-settable options.
- tsdu
A value greater than zero specifies the maximum size of a transport
service data unit (TSDU).
A value of zero specifies that the transport provider does not support
the concept of TSDU, although it does support the sending of a data
stream with no logical boundaries preserved across a connection.
A value of -1 specifies that there is no limit on the size of a TSDU.
A value of -2 specifies that the transfer of normal data is not
supported by the transport provider.
- etsdu
A value greater than zero specifies the maximum size of an expedited
transport service data unit (ETSDU).
A value of zero specifies that the transport provider does not support
the concept of ETSDU, although it does support the sending of
an expedited data stream with no logical boundaries preserved across
a connection.
A value of -1 specifies that there is no limit on the size of an
ETSDU.
A value of -2 specifies that the transfer of expedited data is not
supported by the transport provider.
- connect
A value greater than or equal to zero specifies the maximum amount of
data that
may be associated with the connection establishment functions
t_connect()
and
t_rcvconnect().
A value of -1 specifies that there is no limit on
the amount of data sent during connection establishment.
A value of -2 specifies that the transport provider does not allow
data to be sent with connection establishment functions.
- discon
A value greater than or equal to zero specifies the maximum amount of
data that may be associated with the and functions.
A value of -1 specifies that there is no limit on the amount of data
sent with these abortive release functions.
A value of -2 specifies that the transport provider does not
allow data to be sent with the abortive release functions.
- servtype
This field specifies the service type supported by the transport
provider, as described below.
- flags
This is a bit field used to specify other information about the
transport provider. If the
T_SENDZERO
bit is set in flags, this
indicates the
underlying transport provider supports the sending of zero-length TSDUs.
See Appendix A, "ISO Transport Protocol Information," of the
CAE Specification X/Open Transport Interface (XTI)
manual from X/Open Company Limited
for a discussion of the separate issue of zero-length
fragments within a TSDU.
If a transport user is concerned with protocol independence, the above
sizes may be accessed to determine how large the buffer must be to
hold each piece of information. Alternatively, the
t_alloc()
function may be used to
allocate these buffers. An error will result if a transport user
exceeds the allowed data size on any function.
The
servtype
field of
info
specifies one of the following values on return:
- T_COTS
The transport provider supports a connection-mode service but does not
support the optional orderly release facility.
- T_COTS_ORD
The transport provider supports a connection-mode service with the
optional orderly release facility.
- T_CLTS
The transport provider supports a connectionless-mode service.
For this service type,
t_open()
will return -2 for
etsdu,
connect,
and
discon.
A single transport endpoint may support only one of the above services
at one time.
If
info
is set to a null pointer by the transport user, no protocol
information is returned by
t_open().
Obsolescent Interfaces
When using TCP and UDP through HP XTI,
name
can be
/dev/inet_cots
and
/dev/inet_clts,
respectively. These names are supported for
backward-compatibility purposes. They might not be supported in
future releases, and they should be replaced with
/dev/tcp
and
/dev/udp,
respectively.
Fork Safety
t_open
is not fork-safe.
RETURN VALUE
A valid endpoint identifier is returned upon successful completion. Otherwise,
a value of -1 is returned and
t_errno
is set to indicate an error.
HP OSI does not support the
T_COTS_ORD
servtype.
ERRORS
On error,
t_errno
is set to one of the following:
- [TBADFLAG]
An invalid flag is specified.
- [TBADNAME]
Invalid transport provider name.
- [TSYSERR]
A system error has occurred during execution of this function.
- [TPROTO]
(XTI only) This error indicates that a communication problem has been detected
between XTI and the transport provider for which there is no suitable
XTI (t_errno).
STANDARDS CONFORMANCE
t_open(): SVID2, XPG3, XPG4
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